In general, a photographic processing of silver halide color photographic materials comprises a color developing process and a desilvering process. Silver produced by development is oxidized with a bleaching agent and then dissolved with a fixing agent. As the bleaching agent, ferric ion complex salts (e.g., aminopolycarboxylic acid-Fe(III) complex salts) are commonly used. As the fixing agent, a thiosulfate is employed generally.
On the other hand, a processing step of black-and-white photographic materials comprises a developing process and a removing process of unexposed silver halide. In other words, photographic materials are subjected to fixing after development without bleaching thereby differing from the processing of color photographic materials. Thiosulfates also are used generally as the fixing agent in the processing of black-and-white photographic materials.
In recent years, it is desirable for the processing bath to have a more stable liquid composition in proportion to the reduction in replenishment. In the fixing bath, for example, a sulfite is added as a preservative for preventing oxidation because the thiosulfates usually employed as the fixing agent suffer oxidative deterioration to yield sulfide precipitates. Although an improvement in solution stability is required as further reduction in replenishment is made, the stabilization problem cannot be settled solely by the further addition of sulfites because sulfites also have a solubility problem, or a formation problem of Glauber's salt formed as a precipitate when oxidized and so forth.
Particularly in the photographic processing of silver halide color photographic materials, the bleach-fixing process recently has been carried out using a bleaching agent having higher potential in view of rapidity. Thus, the thiosulfates therein are subject to a more rapid oxidative deterioration.
Accordingly, it is desirable to obtain compounds with a greater capacity in fixability than thiosulfates particularly from the standpoint of increasing the speed of photographic processing. Thus, development of a fixing agent with excellent stability to oxidation and fixability, which can take the place of thiosulfates, has been desired.
However, satisfactory compounds have not been found because compounds which are known as fixing agents other than thiosulfates, namely thiocyanic acid compounds (especially ammonium thiocyanate), thiourea compounds, thioether compounds (e.g., 1,10-dioxa-4,7-dithiadecane) and so on are insufficient in fixability or solubility.
On the other hand, a method for accelerating a bleach-fixing or fixing process by the use of a thioether compound in a bleach-fixing solution or a fixing solution (fixer) is disclosed, e.g., in JP-B-60-24936 (the term "JP-B" as used herein refers to an "examined Japanese patent publication"), JP-A-53-37418 (the term "JP-A" as used herein refers to a "published unexamined Japanese patent application", JP-A-62-129855, JP-A-62-135834, JP-A-62-136651, JP-A-62-136657, JP-A-62-177556, JP-A-54-71634, JP-A-64-21444, JP-A-49-16436, U.S. Pat. Nos. 3,241,966 and 3,716,362, JP-A-2-44355 and so on. However, all of the means adopted therein aimed at stimulating fixation in the presence of thiosulfates. Therefore, such means do not serve one of the purposes of the present invention, that is, heightening solution stability.
U.S. Pat. No 2,748,000 discloses that a thioether compound similar to that of the present invention is used in the bleach-fixing bath as a fixing agent. However, as the similar thioether compound has an insufficient fixing performance and many thermostains (i.e., the stain which is generated under the warm and humid condition) generate after processing, the means does not serve one of the purposes of the present invention.